Electrical apparatus



J. R. CRAIGHEAD.

ELECTRICAL APPARATUS APPLICATION FILED SEPT. 20, 1916;

Inventor James R. Craihead His fittorney.

Patented Dec. 16, 1919.

UNITED STATES PATENT OFFICE.

JAMES R. CBAIGHEAD, OF SCI-IENECTADY, NEW YORK, ASSIGNOR T0 GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRICAL APPARATUS.

Application filed September 20, 1916.

To all whom it may concern:

Be it known that 1, JAMES R. CRAIGHEAD, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements in ElectricalApparatus, of which the following is a specification.

My invention relates to electrical apparatus, and particularly toapparatus for electrically imparting an impulse to a movable member,such, for example, as apparatus for imparting an impulse to a movablecontact for accentuating the engagement of two relatively movablecontacts.

The object of the invention is to provide an improved apparatus forelectrically imparting an impulse to a movable member. Moreparticularly, the object of the inven tion is to provide an improvedcontact accentuating device. Other objects of the invention will bebrought out hereinafter.

The novel features ofthe invention which I believe to be patentable aredefinitely pointed out in the appended claims. The invention itself andthe construction and mode of operation of an apparatus embodying theinvention will be bestnmderstood from the following description taken inconjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic view partly in perspective of a circuitinterrupter embodya ing the invention; and Figs. :2 and 3 areexplanatory detail views,

In Fig. l of the drawing, I have diagrammatically represented anelectrical installation 5, in whose circuit is arranged a circuitbreaker or interrupter (3. The circuit breaker is of the well knownelectromagnetic type having a trip coil 7. The trip coil is designed tobe energized by the engagement of two relatively movable contacts 8 and9, whose relative movement is effected by a time relay.

The contact 8 is fixed, while the contact 9 is secured to a pivotallymounted shaft 10. For the purposes of explanation, I will assume thatthe shaft 10 is to be driven at a uniform speed upon the occurrence of apredetermined overload in the installation but it will, of course, beunderstood that the shaft 10 might equally well be driven at any desiredspeed. as. for example. at a speed proportional to the overload. Thus,

Specification of Letters Patent.

Patented Dec. 16, 1919.

Serial No. 121,335.

I have shown a gear 11 operatively connected to the shaft 10 throughcrown gearing 12, and a gear 13 operatively connected to a clock-drivengear 1 1. The gear 11 may be driven by a clock, as suggested, or by anyother suitable constant speed driving mechanism, such, for example, as aconstant speed electric motor. The gears 11 and 13 are designed to beoperatively connected together by means of a movable gear 15. The gear15.is carried at the end of a pivot-ed arm 16 and is normally held outof engagement with the gears 11 and 13 by means of a spring 20. Thearmature 17 of an electromagnet 18 is secured to the arm 16, and whenthe electromagnet is energized the armature 17 and arm 16 are drawn downuntil the gear 15 meshes with the two gears 11 and 13. The shaft 10 isthen driven by the clock-driven gear 1d at constant speed, and themovable contact 9 moves toward its cooperating fixed contact 8.

A spiral spring 21 secured at one end to the shaft 10 and at its otherend to a fixed pin 22 normally operates to hold the shaft 10 and contact9 in their initial positions, determined by the engagement of thecontact 9 with a fixed stop 23. A current responsive relay 24: isincluded in series with the installation 5, and operates to complete thecircuit of the electromagnet 18 upon the occurrence of a predeterminedoverload in the installation. Thus, upon the occurrence of thepredetermined overload at which it is desired that the contact 9 shouldstart to move toward contact 8, the electromagnet 18 is energized fromany suitable source, such as abatt-ery 25, by the bridging of thecontacts 26. The gear 15 is thereupon drawn into engagement with thegears 13 and 11, and the contact 9 moves at a uniform speed toward thecontact 8. Upon the engagement of these contacts 8 and 9, the improvedcontact accentuating device of my present invention gives an impulse tothe movable cont-act 9, thereby insuring a firm engagement of thecontacts.

My improved contact accentuating device is broadly an electric motorelement which operates upon achange in the value of the current flow inthe current carrying coil 7 secured to the shaft 10 and arranged torotate in the air gap of a magnetic core 28. A. current carrying coil 29is mounted on the core 28 and is electrically connected in seriesrelation with the trip coil 7 and the contacts 8 and 9. A permanentmagnet 30 has its poles arranged on opposite sides of the disk armature27, and is so positioned with respect to the poles of the magnetic core28, that a large portion of any eddy currents set up in the armature 27by a change in the current flowing in the coil 29 cuts the flux of themagnet 80 at right angles.

The operation of the contact accentuating device is as follows :lVhenthe movable contact 9 just engages the stationary contact 8, the circuitincluding the trip coil 7 and coil 29 is completed through the battery25. The current flowing in this circuit increases from zero to aconstant value, determined by the circuit resistance and impressedvoltage. During this increase in the value of the current flow in thiscircuit, there is a corresponding increase in the flux across the polesof the n'iagnetic core 28, and this increase in flux sets up eddycurrents in the disk armature 27. These eddy currents cooperate with theflux of the magnet 30 to produce a motor action, resulting in a slightimpulse to the armature, which operates to accentuate the engagement ofthe contacts 8 and 9. In other words, the device is so designed that anincrease in the flux resulting from the coil 29 tends to move thecontact 9 toward the contact 8.

The contact accentuating device of my present invention merely impartsan impulse to the cooperating contacts at the instant of theirengagement, and then ceases to exert any influence as long as thecontacts remain engaged. This is because the motor action of the devicedepends upon a change in the value of the current flow in the coil 29,and it is only While the value of the current flow in this coil isundergoing a change, that eddy currents are induced in the armature 27.It will be apparent, however, that when the contacts 8 and 9 disengagethe value of the current flow in the coil 29 decreases to zero, and theresulting decrease in the flux across the poles of the magnetic core 28produces eddy currents which react with the flux of the permanent magnet30 to produce an impulse tending to separate the contacts. Thus, theimproved contact accentuator not only operates to secure a betterengagement of the contacts, but also insures a quick break of thecontacts.

The permanent magnet 30 can be dispensed with by mounting ashort-circuiting coil 31 on a portion of the pole face of the magneticcore 28, as illustrated in Fig. 2 of the drawing. The short-cireuitedcoil forms in efl'eet a shaded-pole induction motor element, and ashifting magnetic field is produced by a change in the value of thecurrent flow in the coil 29. This shifting n'lagnetic field only occursduring the change in the current flowing in the coil 29, and hence animpulse is imparted to the contact 9 upon the engagement of this contactwith the fixed contact 8, as well as upon the disengagement of thesecontacts.

From the foregoingdescription it will be seen that my improved impulseimparting device operates only at the instants that impulses areadvantageous. As soon as the need for the impulse is over, the agenciescausing the impulse cease to operate, and hence no continuing force ispresent. In addition to giving an impulse for accentuating theengagement of the contacts, the device also gives an impulse forseparating the contacts. lVhile I have described the device incombination with a time relay and circuit interrupter, it will, ofcourse, be understood that the device may be embodied in any apparatuswhere relatively movable cooperating contacts are used. The coil 29 mayalso be included in a separate circuit controlled by the relativelymovable contacts, instead of being included in the same. circuit as themain actuating device, such as the tripping coil 7. Many otherapplications of my invention besides that specifically mentioned hereinas well as many modifications in the particular embodiment of theinvention herein illustrated and described will be apparent to thoseskilled in the art. 1 wish to cover, therefore, in the appended claimsall applications and modifications of the invention within its genericspirit and scope.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The combination with relatively movable coiiperating electriccontacts of means for in'nnediately accentuating the engagelnent of saidcontacts comprising a rotatable disk armature of conducting materialoperatively connected to one of said contacts, electromagnetic meansoperatively related to said armature, and means including said contactsand said electromagnetic means for imparting to said armature upon theen gagement of said contacts a momentary impulse only tending to movethe contacts into better engagement.

2. The combination with relatively movable cooperating electric contactsof means for immediately accentuating the engagement of said contactscomprising a rotatable disk armature of conducting material,electromagnetic means including a current carrying coil operativelyrelated to said armature, means cooperating with said electromagneticmeans for imparting an impulse to said armature upon a change in thevalue of the current flow in said coil, and

armature tending means for causing a change in the value of the currentflow in said coil upon the engagement of said contacts whereby a momentary impulse only is imparted to said to move the contacts intobetter engagement.

3. The combination with relativelymovable cooperating electric contactsof means for accentuating the engagement of said contacts comprising adisk armature of conducting material, electromagnetic means including acurrent carrying coil operatively related to said armature, meanscooperating with said electromagnetic means for imparting to saidarmature an impulse tending to move said contacts toward each other whenthe value of the current flow in said coil changes in one direction andaway from each other when the value of the current flow in said coilchanges in the other direction, and means for causing the value of thecurrent flow in said coil to change in'the one direction when saidcontacts engage and in thevother direction when said contacts disengage.

4. The combination with relatively movable cooperating electric contactsof means for immediately accentuating the, engagement of said contactscomprising an electric motor element having a current carrying coil andoperatively connected to one of said contacts so as to impart amomentary impulse only to this contact tending to move the contacttoward the other contact upon a predetermined change in the value of thecurrent flow in said coil, and means whereby the engagement of saidcontacts effects such predetermined change in the current flow in saidcoil. c,

5. The combination with a movable member of means for imparting amomentary impulse only to said member comprising a rotatable diskarmature of conducting material operatively related to the member,electromagnetic means including a current carrying coil operativelyrelated to said armature, and means whereby the value of the currentflow in said coil is changed thereby producing a motor action betweensaid electromagnetic means and said armature when it is desired toimpart the momentary impulse to said member.

6. The combination with a-movable member of means for imparting amomentary impulse only to said member comprising an electric motorelement having a current carrying coil and a rotatable armatureoperatively connected to said member, and means whereby the value of thecurrent flow in said coil is changed thereby producing a motor action ofsaid element when it is ]desired to impart the impulse to said mem- 7.The combination with a movable member of means for imparting an impulseto said member comprising an element of conducting material operativelyconnected to said member, means for causing a flow of current in saidelement at the instant it is desired to impart the impulse to saidmember, and means whereby the current flowing -in said element is causedto react with a magnetic flux thereby producing a motor action whichimparts the desired impulse to said member.

8. The combination with relatively movable cooperating electric contactsof means for accentuating the engagement of said contacts comprising adisk armature of conducting material, means for setting up eddy currentsin said disk when said contacts engage, and means .for setting up amagnetic flux and including said last mentioned means whereby the eddycurrents flowing in said disk react with the magnetic flux therebyproducing a motor action which accentuates the engagement of saidcontacts.

In witness whereof, I have hereunto set my hand this 19th day of Sept,1916.

JAMES R. CRAIGHEAD.

